The Tokyo Organizing Committee of the Olympic and Paralympic Games hopes to move forward the start times of the 2020 marathons by one hour to 6 a.m. to avoid the extreme summer heat, sources said Wednesday.

In July, the International Olympic Committee approved the organizers' plan to set the start times for the men's and women's marathons at 7 a.m., 30 minutes earlier than initially slated when Tokyo launched its bid to host the July 24-Aug. 9 Games.

But after a record heatwave in 2018, with temperatures reaching 41.1 C in Kumagaya near the Japanese capital, concerns have grown that similar conditions in 2020 could pose health risks to athletes, spectators and workers.

Organizers have acknowledged the need for further counter-measures against the heat.

"We'd like to officially propose to the IOC and IFs (International Sports Federations) an earlier start," said Toshiaki Endo, vice president of the Tokyo 2020 organizing committee.

The ruling Liberal Democratic Party considered adopting daylight saving time but abandoned the idea, citing technological difficulties in making such a change in less than two years.

In late October, health officials in Japan called for the races to start at 5:30 a.m. to minimize the risk of heatstroke, with the Japan Medical Association and the Tokyo Medical Association warning organizers of possible heat-related deaths.

Marathon races started at 6 a.m. at the Asian Games held in Jakarta in August and at the Beijing Olympics in 2008, which also faced extreme heat as well as air pollution concerns, the marathons began at 7:30 a.m.

The marathon for the Tokyo Olympics will be held on Aug. 2 for women and Aug. 9 for men, the day of the closing ceremony.

The start times for rowing events at the 2020 Games were also brought forward by as much as one hour to 8:30 a.m. on all days except July 31, the last day of competition.